Re: [GIT PULL] Filesystem Information

From: Ian Kent <raven@themaw.net>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: David Howells <dhowells@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Al Viro <viro@zeniv.linux.org.uk>, Karel Zak <kzak@redhat.com>,
	Jeff Layton <jlayton@redhat.com>,
	Miklos Szeredi <mszeredi@redhat.com>,
	Nicolas Dichtel <nicolas.dichtel@6wind.com>,
	Christian Brauner <christian@brauner.io>,
	Lennart Poettering <lennart@poettering.net>,
	Linux API <linux-api@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org,
	LSM <linux-security-module@vger.kernel.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [GIT PULL] Filesystem Information
Date: Wed, 05 Aug 2020 19:13:55 +0800	[thread overview]
Message-ID: <c44b1c225b0aec20969aace1ba1b7900ddda5a5e.camel@themaw.net> (raw)
In-Reply-To: <CAJfpegvQdCr+u51_xkpbS7eMZyNqtnk_tdK1KVhsiCuiFWWJJw@mail.gmail.com>

On Wed, 2020-08-05 at 10:00 +0200, Miklos Szeredi wrote:
> On Wed, Aug 5, 2020 at 3:33 AM Ian Kent <raven@themaw.net> wrote:
> > On Tue, 2020-08-04 at 16:36 +0200, Miklos Szeredi wrote:
> > > And notice how similar the above interface is to getxattr(), or
> > > the
> > > proposed readfile().  Where has the "everything is  a file"
> > > philosophy
> > > gone?
> > 
> > Maybe, but that philosophy (in a roundabout way) is what's resulted
> > in some of the problems we now have. Granted it's blind application
> > of that philosophy rather than the philosophy itself but that is
> > what happens.
> 
> Agree.   What people don't seem to realize, even though there are
> blindingly obvious examples, that binary interfaces like the proposed
> fsinfo(2) syscall can also result in a multitude of problems at the
> same time as solving some others.
> 
> There's no magic solution in API design,  it's not balck and white.
> We just need to strive for a good enough solution.  The problem seems
> to be that trying to discuss the merits of other approaches seems to
> hit a brick wall.  We just see repeated pull requests from David,
> without any real discussion of the proposed alternatives.
> 
> > I get that your comments are driven by the way that philosophy
> > should
> > be applied which is more of a "if it works best doing it that way
> > then
> > do it that way, and that's usually a file".
> > 
> > In this case there is a logical division of various types of file
> > system information and the underlying suggestion is maybe it's time
> > to move away from the "everything is a file" hard and fast rule,
> > and get rid of some of the problems that have resulted from it.
> > 
> > The notifications is an example, yes, the delivery mechanism is
> > a "file" but the design of the queueing mechanism makes a lot of
> > sense for the throughput that's going to be needed as time marches
> > on. Then there's different sub-systems each with unique information
> > that needs to be deliverable some other way because delivering
> > "all"
> > the information via the notification would be just plain wrong so
> > a multi-faceted information delivery mechanism makes the most
> > sense to allow specific targeted retrieval of individual items of
> > information.
> > 
> > But that also supposes your at least open to the idea that "maybe
> > not everything should be a file".
> 
> Sure.  I've learned pragmatism, although idealist at heart.  And I'm
> not saying all API's from David are shit.  statx(2) is doing fine.
> It's a simple binary interface that does its job well.   Compare the
> header files for statx and fsinfo, though, and maybe you'll see what
> I'm getting at...

Yeah, but I'm biased so not much joy there ... ;)

Ian